It is conventional to mount a rotary switch on the transmission housing externally thereof to receive mechanical gear selection inputs from the operator of a vehicle through various linkages and output gear selections to a decoder module and the transmission electronic control unit via electronic signals. The switch includes a quadrant with a selected number of electrical switch segments disposed thereon with each segment providing an output to the decoder module. The manual valve controlling hydraulic operation of the transmission is mechanically coupled to a plate having indexing detents, called a detent lever, mounted on a shaft and pivotably movable therewith. The shaft extends through the transmission housing wall and a switch bar is fixedly attached to the shaft externally of the transmission housing so that when a vehicle operator selects a gear the switch bar within the rotary switch moves across the quadrant to a predetermined position to engage one or more of the electrical contact segments. In certain systems the electronic control monitors the gear position along with other inputs relative to such things as throttle position, output shaft speed, engine speed, engine load and so on.
In copending application Ser. No. 07/978,603, now U.S. Pat. No. 5,338,907, assigned to the assignee of the present invention, a switch system is disclosed which is mounted within the transmission housing in order to avoid placing the switches in a hostile environment subject to water splash and the like as well as to avoid tolerance stack-up problems associated with linkages employed when mounting the switches externally of the transmission housing. In that application a switch housing is shown mounted on the manual lever shaft. The housing is coupled to the roller attached to the detent spring biasing the roller into engagement with the outer edge of the detent lever to maintain the housing stationary relative to the transmission housing. A switch arm fixedly mounted to the manual lever shaft mounts a plurality of first electrical contacts and extends into the switch housing. The switch arm, movable with the detent lever, moves into and out of engagement with respective second electrical contacts mounted on the switch housing. Annular seals are disposed between a hub of the switch arm and the switch housing to prevent ingress of metal particles and debris into the switch housing.
Switch systems made in accordance with application Ser. No. 07/978,603, now U.S. Pat. No. 5,338,907 are very effective in obviating the prior art hostile environment and stack-up problems; however, in certain vehicles the space available to place a switch system within the transmission housing, especially in the direction taken along the longitudinal axis of the manual lever shaft, i.e., in a vertical direction, is so limited that there is insufficient space for conventional seal mechanisms needed to prevent ingress of metal particles and other debris into the switch housing.
It is therefore an object of the invention to provide an electric switching assembly responsive to gear selection which is free of the limitations of the prior art mentioned above and which can be fitted within available space of existing vehicular transmission housings. Another object of the invention is the provision of a switch assembly having a rotary member with an improved mechanism which allows passage of fluid but prevents ingress of debris and which occupies minimal space, particularly in the vicinity of the manual lever shaft, yet which is reliable and has a long useful life.
Other objects, advantages and details of the switch system of this invention and seal mechanism therefore, appear in the following detailed description of preferred embodiments of the invention.